On Tue, 17 Apr 2012, Paul Zimmerman wrote: > Hi Alan, > > > The ehci-hcd driver is a little haphazard about keeping track of the > > state of the USBCMD register. The ehci->command field is supposed to > > hold the register's value (apart from a few special bits) at all > > times, but it isn't maintained properly. > > > > This patch (as1543) cleans up the situation. It keeps ehci->command > > up-to-date, and uses that value rather than reading the register from > > the hardware whenever possible. > > @@ -347,6 +352,7 @@ static int ehci_reset (struct ehci_hcd * > > if (ehci->debug) > > dbgp_external_startup(); > > > > + ehci->command = ehci_readl(ehci, &ehci->regs->command); > > Wouldn't it be a good idea to mask off bits that cannot be cleared > by software (like CMD_IAAD) whenever ehci->command is read from the > register? Otherwise, if a bit has been set but not cleared by the > hardware yet, that bit would get set again the next time you use > the contents of ehci->command. Maybe, but it doesn't seem very necessary. After all, the controller has just completed a software reset, so none of those exotic bits should be turned on. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
